The output voltage-versus-temperature characteristics of many temperature detectors, such as thermocouples or thermistors, are non-linear and unique, and their calibration curves are likewise non-linear and unique.
Linearisation circuitry is necessary to convert the non-linear curves to linear curves so that, for example, one millivolt of output voltage will be equivalent to 1° Centigrade or 1° Fahrenheit of measured temperature.
In addition, the linear or linearised curves may possess zero offsets, so that corrective circuitry is required.
Furthermore, some temperature detectors, such as thermocouples, may require a constant temperature reference, and this may be provided, for example, by cold junction compensation circuitry.
U.S. Pat. No. 6,074,089 (Omega Engineering, Inc.), incorporated herein by reference, discloses a hand-held connector module which contains the foregoing signal conditioning circuitry and a battery which powers the circuitry. The module is provided with input and output connectors which are respectively connected, via appropriate external leads, to a temperature detector and the test meter or other apparatus which utilises the temperature measurement signals.